Potato protein equaled milk protein for muscle building. That finding landed online and stayed — shared, screenshotted, cited in every plant-protein debate since. Thirty grams of potato concentrate against thirty grams of milk in a direct trial. Muscle-building activity was statistically identical. The amino acids explain the tie: potato concentrate delivers nearly the same leucine trigger as milk, the same essential amino acid load, gram for gram.
Nothing about that headline was wrong. The trial was rigorous, the journal top-tier, the finding real. What the headline never included was the word concentrate.
Is potato protein as good as animal protein for building muscle?
Potato protein concentrate equaled milk protein in a direct five-hour muscle-building trial, but acute signals poorly predict long-term growth. No long-term study has tested potato protein on its own. Across the available evidence, non-soy plant proteins as a group gained less muscle than animal protein.
— Pinckaers et al. 2022 · Med Sci Sports Exerc · n=24; Reid-McCann et al. 2025 · Sports Med · 43 RCTs
The protein in that trial was Solanic 100 — a purified extract manufactured from potato starch waste, refined to eighty-two percent protein by weight. Not potatoes. A processed ingredient as removed from the vegetable as whey powder is from the milk it started as. To get the same thirty grams from whole potatoes, you would need more than two kilograms in one sitting.
That distinction matters less, though, than the measurement itself. Building muscle takes months. One post-workout measurement takes five hours. That mismatch — five hours versus five months — dissolves the headline's confidence entirely. The snapshot looked identical for potato and milk. Whether it means anything when someone trains on potato protein for a real block — that experiment has never taken place.
A five-hour muscle-building snapshot is a poor predictor of whether muscle actually accumulates across a training cycle.
Across every long-term trial comparing non-soy plant proteins to animal protein for actual muscle gained, the plant side fell behind by a meaningful margin in five studies. Potato was in that pool, alongside rice, oat, and chia. None were estimated separately. Soy is the only plant protein with enough long-term evidence to match animal protein — seventeen trials deep. Potato has zero.
The trial that started the headline drew partial funding from the potato industry — an advocacy group and the company that manufactured the concentrate. The science was rigorous. The data was clean. The funding explains why a single five-hour result in twenty-four young men traveled further than meta-analyses pooling decades of evidence.
Potato concentrate triggers the same muscle-building signal as milk inside a single post-workout window. Whether it delivers the same results across months of training is something no trial has measured. The broader evidence — whether plant protein as a category keeps up with animal protein for long-term muscle — has more to say, and the answer changes with every plant on the list.